[45.03] Probing the central parsecs of AGN using Faraday Rotation

R.T. Zavala (New Mexico State University, NRAO), G.B. Taylor (NRAO)

A broad frequency range and low instrumental polarization
makes the Very Long Baseline Array (VLBA) an ideal
instrument for studying polarimetry at sub-milliarcsecond
resolution. To take advantage of these unique capabilities
we have conducted a multi-frequency polarization survey of
40 radio-loud AGN (Quasars, BL Lacs, and radio galaxies).
Our aim is to use Faraday Rotation Measures (RMs) as a probe
of the central 1-50 parsecs of these objects. The RM is
produced by the line of sight magnetic field weighted by the
electron density. Using the electron density established
through spectral line diagnostics a magnetic field strength
and topology can be estimated within a few parsecs of the
central engines of these AGN.

The observations for the survey are complete, and we present
the first results for 8 quasars, 5 BL Lacs, and 4 radio
galaxies. The magnitudes for the RMs range from several
thousand rad m-2 in the quasars and radio galaxies to a
few hundred rad m-2 in the BL Lac objects. These values
are in agreement with the basic ideas of the unified model
for AGN. We also observe variations in the RM on small
spatial (\lesssim 1 pc) in radio galaxies and quasars; and
short time scales (~ 6 months) in the quasars 3C 273
and 3C 279.

R.T.Z. gratefully acknowledges support from a pre-doctoral
research appointment at NRAO and from the New Mexico
Alliance for Graduate Education and the Professiorate
through NSF grant HRD-0086701.

The author(s) of this abstract have provided an email address
for comments about the abstract:
rzavala@nrao.edu